It would be a breaking change since it modifies the behavior of `throws`
without a type parameter. It would also be incompatible with the declaration of
methods in protocols.
Félix
> Le 28 août 2016 à 01:44:27, Bouke Haarsma via swift-evolution
> <swift-evolution@swift.org> a écrit :
>
> On 2016-08-26 15:39:05 +0000, Félix Cloutier via swift-evolution said:
>
> Hi all,
>
> Currently, a function that throws is assumed to throw anything. There was a
> proposal draft last December to restrict that. The general idea was that
> you'd write, for instance:
>
>
> enum Foo: ErrorProtocol {
> case bar
> case baz
> }
>
> func frob() throws Foo {
> throw Foo.bar // throw .bar?
> }
>
> If you `catch Foo` (or every case of Foo), now that the compiler can verify
> that your catch is exhaustive, you no longer have to have a catch-all block
> at the end of the sequence.
>
> This impacts the metadata format and has implications on resilience, which
> leads me to believe that the discussion could qualify for the phase 1 of
> Swift 4. If this is the case, I'd be interested in pulling out the old
> discussions and seeing where we left that at.
> Félix
>
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>
>
> Hi,
>
> Shouldn't the compiler be able to infer the types thrown, and thus whether
> all types have been thrown? The general idea being that the following would
> be valid:
>
> enum Foo: Error {
> case bar
> case baz
> }
>
> func hello() throws { // inferred to throw only "Foo.bar"
> throw Foo.bar
> }
>
> func world() throws { // inferred to throw only "Foo.baz"
> throw Foo.baz
> }
>
> func galaxy() throws { // inferred to throw only "Foo.baz"
> do {
> try hello()
> } catch Foo.bar {
> // ...
> }
> // catch is exhaustive, no catch-all clause needed
>
> try world()
> }
>
> func universe() { // all errors are handled, no 'throws' declaration needed
> do {
> try galaxy()
> } catch Foo.baz {
> // ..
> }
> // catch is exhaustive, no catch-all clause needed
> }
>
> Now for clarity one could add the type information as per your proposal, but
> wouldn't be necessary as the compiler would infer it itself.
>
> Either way a +1 from me, as the current model forces one to catch-all errors,
> even the ones you did not expect to be thrown. Thus potentially hiding
> programming errors.
>
> - Bouke
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